The human Gene Mapping project involves intramural and extramural collaborations with several groups of the scientific community. The Genetics Section has developed efficient facilities for establishing and maintaining this program through different approaches and methodologies. These include (1) the creation and maintenance of a hybrid cell panel, following hybridization of somatic cells of human and rodent origins and hybrid selection in special culture media; (2) biochemical and karyological characterizations of cell lines; (3) in situ hybridization of molecular clones to human metaphase chromosomes; (4) detection of restriction fragment length polymorphisms by screening human DNAs; and (5) linkage estimation using polymorphic human loci and placing genes on chromosome maps in the context of the Centre D'Etude du Polymorphisme Humain (CEPH) collaboration. Other techniques have also included the use of polymerase chain reaction amplification and electrophoretic analysis of RNA or protein binding products. Altogether these approaches have enabled us to map a number of disparate products such as proto-oncogenes, growth factors, tumor-related products, cell receptors, members of the immunoglobulin superfamily, and chemotactic substances. The principal investigator serves in the human genome projects as an elected member of the Human Genome Organization as well as chairman of the International Committee on Comparative Gene Mapping. Status of ongoing collaborative projects are listed in tabular form in the Project Description of this report.